1. Field of the Invention
The present invention relates to a stacked package of semiconductor package units and a manufacturing method therefor in which a number of semiconductor package units can be stacked, and more particularly, to a stacked package of semiconductor package units and a stacking method therefor, in which a number of semiconductor packages can be efficiently stacked, by directly connecting respective leads of upper and lower semiconductor packages forming the stacked package with one another, without using separate means for connecting respective leads of the semiconductor packages with one another.
2. Description of the Related Art
Most of devices include semiconductor packages performing a variety of functions to form an circuit. In general, the semiconductor packages are surface-mounted on a printed circuit board (PCB) by the piece. However, since various devices become compact with the development of technologies, and a demand for miniaturization also increases, technologies of mounting a number of components on a unit surface, among which a stack packaging technology for mounting a number of semiconductor packages on an identical area and improving an efficiency of mounting the semiconductor packages is particularly swiftly developed and approaches to an practical stage.
A conventional technology for a stacked package will be described with reference to FIGS. 1A and 1B. FIG. 1A is a perspective view of a conventional stacked package and FIG. 1B is a cross-sectional view taken along a line r-r' of FIG. 1A.
As depicted, a conventional stacked package is formed by electrical connection between a number of leads (which are called pins) of respective semiconductor packages IC.sub.A and IC.sub.B to be connected to each other using separate auxiliary means which are called headers H1-H20 in which two semiconductor packages IC.sub.A and IC.sub.B are located in the upper portion and the lower portion, respectively, that is, one on top of the other so that the respective leads face one another. For the operation of the respective semiconductor packages IC.sub.A and IC.sub.B forming a stacked package, when a connection between leads P19.sub.A and P19.sub.B of the semiconductor packages IC.sub.A and IC.sub.B should be blocked like a H19 header, an intermediate portion of the header H19 is cut and the remaining portion of the header H19 transverses the upper portion of the stacked package, to be connected to opposite desired leads. By doing so, in the case that a semiconductor package unit is a 64M synchronous dynamic random access memory (SDRAM), a stacked package having a capacity of 128M SDRAM is formed on the similar mounting area using two semiconductor packages IC.sub.A and IC.sub.B.
However, the above conventional stacked package should contain a number of headers H1-H20 as many as the number corresponding to a number of leads for electrical connection between the corresponding leads, and removes an inter-lead connection portion in the H19 header for electrical disconnection between particular leads. As a pitch between leads, that is, an interval between adjacent two leads becomes narrow with the development of technology, it is difficult and inconvenient to form a stacked package. Moreover, there is a problem that a parasitic capacitance and impedance increase due to headers, so that such an increase influences an operational frequency of the stacked package.
Also, since headers are attached at the state where leads of the semiconductor packages IC.sub.A and IC.sub.B are deformed in shape in the conventional stacked package, as shown in FIG. 1A, after being fabricated in the form of a package, the width of the completed stack package becomes larger than that of a package unit, to thereby cause a mounting area to increase.